[PATCH 04/12] util: set the name for the 'main' thread

Daniel P. Berrangé via Devel posted 12 patches 2 weeks, 5 days ago
There is a newer version of this series
[PATCH 04/12] util: set the name for the 'main' thread
Posted by Daniel P. Berrangé 2 weeks, 5 days ago
The default main thread name is undefined, so use a constructor to
explicitly set it to 'main'. This constructor is marked to run early
as the thread name is intended to be used in error reporting / logs
which may be triggered very early in QEMU execution.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 util/qemu-thread-posix.c | 12 ++++++++++++
 util/qemu-thread-win32.c |  6 ++++++
 2 files changed, 18 insertions(+)

diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 7c985b5d38..121d7ed69b 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -22,6 +22,18 @@
 #include <pthread_np.h>
 #endif
 
+static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
+qemu_thread_init(void)
+{
+# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
+    pthread_setname_np(pthread_self(), "main");
+# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
+    pthread_setname_np("main");
+# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
+    pthread_set_name_np(pthread_self(), "main");
+# endif
+}
+
 static void error_exit(int err, const char *msg)
 {
     fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index 9595a5b090..5e6ca0c12f 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -332,6 +332,12 @@ static void set_thread_description(HANDLE h, const char *name)
     SetThreadDescriptionFunc(h, namew);
 }
 
+static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
+qemu_thread_init(void)
+{
+    set_thread_description(GetCurrentThread(), "main");
+}
+
 void qemu_thread_create(QemuThread *thread, const char *name,
                        void *(*start_routine)(void *),
                        void *arg, int mode)
-- 
2.50.1


Re: [PATCH 04/12] util: set the name for the 'main' thread
Posted by Dr. David Alan Gilbert 2 weeks, 5 days ago
* Daniel P. Berrangé (berrange@redhat.com) wrote:
> The default main thread name is undefined, so use a constructor to
> explicitly set it to 'main'. This constructor is marked to run early
> as the thread name is intended to be used in error reporting / logs
> which may be triggered very early in QEMU execution.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  util/qemu-thread-posix.c | 12 ++++++++++++
>  util/qemu-thread-win32.c |  6 ++++++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index 7c985b5d38..121d7ed69b 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -22,6 +22,18 @@
>  #include <pthread_np.h>
>  #endif
>  
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +qemu_thread_init(void)
> +{
> +# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> +    pthread_setname_np(pthread_self(), "main");
> +# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
> +    pthread_setname_np("main");
> +# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
> +    pthread_set_name_np(pthread_self(), "main");
> +# endif

Should this three way ifdef not be broken out somewhere;
it's already in qemu_thread_start() (and it looks like qjack_thread_creator
should use it)
(and the setname/set_name variety is hilarious).

Other than,


Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>

> +}
> +
>  static void error_exit(int err, const char *msg)
>  {
>      fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
> diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
> index 9595a5b090..5e6ca0c12f 100644
> --- a/util/qemu-thread-win32.c
> +++ b/util/qemu-thread-win32.c
> @@ -332,6 +332,12 @@ static void set_thread_description(HANDLE h, const char *name)
>      SetThreadDescriptionFunc(h, namew);
>  }
>  
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +qemu_thread_init(void)
> +{
> +    set_thread_description(GetCurrentThread(), "main");
> +}
> +
>  void qemu_thread_create(QemuThread *thread, const char *name,
>                         void *(*start_routine)(void *),
>                         void *arg, int mode)
> -- 
> 2.50.1
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/
Re: [PATCH 04/12] util: set the name for the 'main' thread
Posted by Daniel P. Berrangé 2 weeks, 4 days ago
On Tue, Aug 19, 2025 at 11:18:00PM +0000, Dr. David Alan Gilbert wrote:
> * Daniel P. Berrangé (berrange@redhat.com) wrote:
> > The default main thread name is undefined, so use a constructor to
> > explicitly set it to 'main'. This constructor is marked to run early
> > as the thread name is intended to be used in error reporting / logs
> > which may be triggered very early in QEMU execution.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >  util/qemu-thread-posix.c | 12 ++++++++++++
> >  util/qemu-thread-win32.c |  6 ++++++
> >  2 files changed, 18 insertions(+)
> > 
> > diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> > index 7c985b5d38..121d7ed69b 100644
> > --- a/util/qemu-thread-posix.c
> > +++ b/util/qemu-thread-posix.c
> > @@ -22,6 +22,18 @@
> >  #include <pthread_np.h>
> >  #endif
> >  
> > +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> > +qemu_thread_init(void)
> > +{
> > +# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> > +    pthread_setname_np(pthread_self(), "main");
> > +# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
> > +    pthread_setname_np("main");
> > +# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
> > +    pthread_set_name_np(pthread_self(), "main");
> > +# endif
> 
> Should this three way ifdef not be broken out somewhere;
> it's already in qemu_thread_start() (and it looks like qjack_thread_creator
> should use it)

Oh dear, I missed that jack-audio wasn't using our thread creation
wrapper :-(  Yes, we could split this into a helper function.


With regards,
Daniel
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